We spent 2 nights on Mykonos after taking the high-speed ferry from Santorini. We shopped and did some sightseeing, chartered a yacht, ate at a few wonderful restaurants, experienced the nightlife, and visited many hotels. Our favorite restaurants were Katrin and the restaurant at Bill & Coo Suites. We also loved dancing the night away at Jackie O Bar and Caprice.
If taking the high-speed ferry to one of the Greek islands, absolutely upgrade to the VIP/Premium level. The cost difference is minimal and the amenities are very comfortable! Also, if you want to avoid the notorious party-scene on Mykonos, visit during the spring or late summer/early fall when the crowds are much smaller but the weather is still warm.